Fig 5. Ferritin enhances iron toxicity and doesn’t show enhanced iron storage in yeast.

(A) Yeast cells with empty vector (Vector) or expressing ferritin were grown in YNB glucose for 24 hrs and then inoculated in YNB galactose for 18hrs in absence or presence of a 10 fold excess of iron (FeCl₃). The cells were harvested, and total iron content was determined using a ferrozine-based colorimetric assay. Relative iron content found in yeast cells (Vector) growing in YNB galactose media (1 = 5.2 ± 0.4 ng iron/10⁸ cells). The mean of the triplicate experiment was calculated, and the experiment was repeated 3 times. *, indicates significant difference from the values obtained when grown in the absence and the presence of 10 fold excess iron (p <0.05). (B) Spot assay was used to assess the ability of yeast cells expressing ferritin to grow when spotted on YNB galactose alone (control) or with 2mM copper (CuSO₄) or with 6mM iron (FeCl₃). These plates were incubated at 30°C for 3 days.